The present invention generally relates to wireless communication systems, and particularly relates to reducing transient effects in radio link control measurements.
Various entities within wireless communication networks typically make ongoing control measurements with respect to the radio links supported by those networks. For example, base stations commonly perform ongoing measurements for each of the radio links between the base station and one or more remote mobile stations that are communicatively coupled to the base station via those radio links. Exemplary control measurements include received signal quality, e.g., strength, signal-to-interference ratio, error rate, etc., and round trip delay values.
Round trip delay measurements are key in properly managing hard handoff of the mobile stations to neighboring base stations as a function of distance, while signal quality measurements typically are used in managing radio link power and/or traffic channel data rates. Regardless of the specific control parameter or parameters being measured for the link, and regardless of the particular control response involved, the highly dynamic nature of the radio links themselves stands as a significant challenge to making such measurements in a manner that yields stable and appropriate control responses.
For example, essentially all such radio links are subject to multipath phenomena that can cause potentially dramatic and rapidly changing shifts in control measurements. Signal strength might, for example, fluctuate significantly over short periods of time in a severe fading environment. Similarly, measured round trip delay values for a given radio link might shift dramatically on an essentially instantaneous basis as the propagation path lengths change with changing fading conditions. One imagines, for example, the potentially dramatic but short lived shift in measured round trip delay values for a mobile station that quickly moves through the radio shadow of a billboard, building, hill, or other obstruction.
Some provisions generally exist for conditioning these types of control measurements with respect to measurement discontinuities arising from multipath and other phenomena. For example, in at least some instances, certain types of control measurements are subjected to simple filtering processes that average or otherwise dampen large, disruptive changes in measured control parameters. However, it is believed that such provisions fall short of effectively suppressing spurious control measurements.